Abstract
Polymer and surfactant complexation was investigated in systems containing anionic biopolymers and cationic surfactants by various classical and modern methods. Differently charged carrageenans (one, two or three sulfate groups per monomeric unit) and dodecylammonium chloride (DDACl) were used as model systems. Formation of various soluble and insoluble complexes (from nano- to microdimensions) and gelation strongly depends on carrageenan and DDACl concentrations, their molar ratio and linear charge density on carrageenan chains. The main factors governing complexation include electrostatic and hydrophobic interactions as well as conformation of carrageenan chains. With increasing carrageenan concentration, the intramacromolecular complexes change to intermacromolecular, which subsequently reorganize into better ordered structures, giant vesicles, and precipitated stoichiometric compounds, dodecylammonium carrageenates. Structural analysis of the new compounds revealed the formation of a lamellar structure with the polar sublayer containing carrageenan chains and the non-polar sublayer consisting of disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. At gelling carrageenan concentration, progressive addition of DDACl caused gradual transitions from the structure of carrageenan gel alone to lamellar ordering of collapsed gel balanced by intermolecular forces within the gel network, i.e., by hydrogen bonding, electrostatic, hydrophobic and van der Waals forces.
Transformations of PTCDA structures on rutile TiO2 induced by thermal annealing and intermolecular forces
